The older imperials ('73 and older) uses the 5 on 5" bolt pattern. The '74-78 Imperials all use the 5 on 4.5” bolt pattern.
The ’74-76 Imperial uses a normal 9¼” rear differential – and the disk brakes can be pretty easily be adapted to our cars – but there is one major problem. Brake rotors and other parts are no longer available and haven’t been for a long time.
Thirty years ago, my brother installed that setup on his ’77 Dodge ½ ton pickup he had and it worked great. A few years later it was complaining that he couldn’t find replacement parts for it (twenty five years ago). I think he sold his pickup shortly afterwards.
I was told by a factory rep, way back then, the only reason Chrysler installed the rear disks, were to compete against the Lincolns and such at the time. He told me there was no benefit to car by using 4 wheel disk brakes on those heavy cars. He also said they were troublesome, and in some cases, Chrysler paid to get them converted back to drum brakes. No first-hand knowledge about any conversions that were made. All on this paragraph is all second hand information.
I really dislike bumper jacks.
In many cases – they are a disaster just waiting to happen (like after you stick you head under a fenderwell).
Scissor jacks are not much better.
Matter of fact, a month ago, I had a flat on the rear my ’86 5th Ave - a big cut on the sidewall.
I loosened the old wheel, jacked car up, removed the tire, went to trunk to remove the never-touched-the ground-before spare, so I put my knee on the bumper (for leverage) to pull the spare out of the front of trunk.
Putting my knee on bumper – pushed the car forward and car fell off of the jack - in slow motion (with old tire already off of car). At this point, I had about 30 co-workers watching me and all were giggling at my expense when it happened.
Sigh – some days you are the bug, other days you are the windshield.
BudW